Human Acute Myeloid Leukaemia (AML) is an aggressive cancer of white blood cells and is the most common adult acute leukaemia. In more detail, AML is a cancer of the myeloid line of blood cells. It is characterized by the rapid growth of an abnormal white blood cell population. Approximately 80% of AML patients are over the age of 60 and the overall survival of this patient group lies at only approximately 5%.
AML can be classified into several subgroups. By way of example, classification according to the World Health Organization (WHO) criteria is based on examination of bone marrow aspirate or a blood sample via light microscopy. Alternatively, bone marrow or blood may be tested for chromosomal translocations by routine cytogenetic methods or fluorescent in situ hybridisation (FISH), and for specific genetic mutations (such as mutations in the FLT3, NPM1 and CEBPA genes) may be detected by polymerase chain reaction (PCR). Immunophenotyping is another method that may be used to identify the AML subtype, which involves detection of cell surface and cytoplasmic markers using flow cytometry.
Flow cytometry is a technique for counting and examining microscopic particles such as cells by suspending them in a stream of fluid and capturing the light that emerges from each cell as it passes through a laser beam. Cell surface molecules often referred to as “cluster of differentiation” (CD) molecules may be exploited in flow cytometry to characterise cell populations. For example, in fluorescence-activated cell sorting, a diagnostic antibody (labelled with a fluorophore) is employed, which binds to a surface molecule (e.g. a CD molecule) present on and characteristic of the cell population in question. Thereafter, the flourophore (attached to the antibody) is activated by a laser beam and the fluorescence signal detected by the flow cytometer. In this manner, fluorescently-labelled antibodies can be used to detect and sort cells displaying a specific CD molecule (or set of CD molecules).
Current AML therapies typically involve induction chemotherapy followed by post-induction therapy. The goal of induction chemotherapy is to reduce the amount of leukaemic cells to less than 5% of all the nucleated cells in a bone marrow sample. Regrettably, this level of reduction of leukaemic cells is not enough to prevent disease recurrence (i.e. relapse) and almost all patients relapse without post-induction therapy. Post-induction therapy typically involves further cycles of chemotherapy, and in some cases, a hematopoietic stem cell transplant that aims to eliminate minimal residual disease (MRD). MRD is the population of leukaemic cells that is recaltricant to therapy. It is thought that this population of cells contains a sub-population of cells termed a leukaemic stem cell (LSC) population. Acute myeloid leukaemia (AML) leukaemic stem cells (LSC) are a sub-population of cells that propagate leukaemia and have self-renewal properties. They are often resistant to current treatment methods and serve to sustain disease.
Current methods used to detect MRD/LSC include real time quantitative PCR (RQ-PCR) or multi-parameter flow cytometry (MFC). However, current RQ-PCR based MRD/LSC assessment is not possible in approximately half of patients with AML.
In addition, and despite recent technical developments, there is still a lack of a validated MFC methodology demonstrating clinical utility—current sensitivity levels of MFC are at least 1 log below real time that of RQ-PCR assays.
There is, therefore, a need to provide an alternative and/or improved methods for detecting acute myeloid leukaemia leukaemic stem cells. In addition, there is a need to provide an alternative and/or improved method for diagnosis and/or prognosis of acute myeloid leukaemia. In particular, there is a need to provide an alternative and/or improved method to detect and monitor MRD/LSC for acute myeloid leukaemia.
The present invention solves one or more of the above mentioned problems.